This invention mainly relates to a lead frame for use in fabrication of a solid electrolytic capacitor of a facedown terminal type (hereinafter referred to as a “face-down terminal solid electrolytic capacitor”) having electrodes directly drawn out or led out to a board mount side and further relates to a method of manufacturing a face-down terminal solid electrolytic capacitor using the lead frame and a face-down terminal solid electrolytic capacitor manufactured by the method.
Solid electrolytic capacitors using tantalum, niobium, or the like as a valve-action metal are small in size, large in capacitance, and excellent in frequency characteristic and, therefore, have been widely used, for example, in decoupling circuits and power supply circuits of CPUS. With the recent development of portable electronic devices, commercialization is increasingly made of a face-down terminal solid electrolytic capacitor having electrodes directly drawn out to a board mount side and having a small ESR (equivalent series resistance) and a small ESL (inductance component) of the entire capacitor particularly in a high frequency band.
Such a face-down terminal solid electrolytic capacitor is disclosed, for example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2003-133177 (Patent Document 1). The capacitor is manufactured as follows. A case is prepared which includes an anode portion and a cathode portion facing each other and having lower ends connected to each other by a coupling portion. A capacitor element is disposed between the anode and the cathode portions so as to be electrically connected thereto. After covering an area between the anode and the cathode portions with a synthetic resin, the coupling portion is ground or removed to electrically separate the anode and the cathode portions from each other and to expose parts of the anode and the cathode portions that are adapted to be faced to a circuit board.
Another face-down terminal solid electrolytic capacitor is disclosed, for example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2004-349270 (Patent Document 2). In the capacitor, cathode exposed portions exposed from a casing resin are provided at least two positions on the same plane with respect to a cathode terminal.
However, the above-mentioned face-down terminal solid electrolytic capacitors are disadvantageous in electrode terminal structure. Specifically, a current path distance between the anode and the cathode or a conducting path distance from the capacitor element to the circuit board is considerably long. Further, the skin depth decreases in a high frequency band. Therefore, the ESR (equivalent series resistance) and the ESL (inductance component) of the entire capacitor remarkably increase. Thus, it is not possible to achieve sufficiently low values of ESR and ESL of the entire capacitor.